PISTIS: From a Word-of-Mouth to a Gentleman’s Agreement

The accelerated digitalisation of society along with
technological evolution have extended the geographical span
of cyber-physical systems. Two main threats have made the
reliable and real-time control of these systems challenging: (i)
uncertainty in the communication infrastructure induced by
scale, openness and heterogeneity of the environment and devices;
and (ii) targeted attacks maliciously worsening the impact of
the above-mentioned communication uncertainties, disrupting the
correctness of real-time applications.
This paper addresses those challenges by showing how to build
distributed protocols that provide both real-time with practical
performance, and scalability in the presence of network faults
and attacks. We provide a suite of real-time Byzantine protocols,
which we prove correct, starting from a reliable broadcast
protocol, called PISTIS, up to atomic broadcast and consensus.
This suite simplifies the construction of powerful distributed
and decentralized monitoring and control applications, including
state-machine replication. Extensive empirical evaluations show-
case PISTIS’s robustness, latency, and scalability. For example,
PISTIS can withstand message loss (and delay) rates up to 40%
in systems with 49 nodes and provides bounded delivery latencies
in the order of a few milliseconds.